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AutomatedBuildings.com Publishes Article About Addressable Lighting Controls

By Lighting Controls Association, on June 1, 2011

Terry Mocherniak, Chief Operating Officer for Encelium Technologies, contributed an article to AutomatedBuildings.com about addressable lighting controls and specifically Encelium’s Energy Control System™.

“Projections indicate that energy-efficient lighting products will make up over three-quarters of the U.S. lighting market by 2020.

These state-of-the-art lighting systems have been available for years and are now reaping a new level of respect and acceptance, which they so deserve. One such product is Encelium’s Energy Control System™ (ECS), the market’s leading addressable dimming system specifically designed for energy management that has been installed in more than 35 million square feet worldwide.”

Check it out here.

Control Wiring: A Primer

By Craig DiLouie, on October 15, 2010

Control wiring provides a path for command and status communication between control devices in a lighting and control system and, in many cases, power to the devices as well.

“Control wiring is the medium by which a user communicates a desired level to the lighting device,” says Thomas Hinds, Product Manager-Fluorescent Dimming Ballasts for Lutron Electronics Co., Inc. “The choice of control wiring is important to ensure signal quality, minimize noise and interference, and meet electrical codes.”

Wiring is interrelated with overall lighting control system considerations—such as selection of control system and components, layout and installation practices—and is therefore an important consideration when choosing a lighting control solution.

Line voltage wiring

Line-voltage (Class 1) wiring provides power (120-277VAC) and load connectivity for lighting equipment as well as, optionally, ground, neutral and travelers for multiway applications. Conventionally, line-voltage wiring has provided the means for grouping light fixtures by circuit/switch-leg to create control zones. The lights are switched ON/OFF using a controller that closes or opens the circuit to provide or deny electric power. The wiring can be used for powerline carrier communication of raise/lower (dimming) as well as switching signals.

Pros: Line-voltage wiring is very familiar to electrical workers and therefore less prone to installation error, can provide both power and communication, can be run with other line-voltage wiring in the same conduit, and can be installed in long runs. It is particularly suitable for retrofit applications if the existing line-voltage wiring is already properly located and is being used.

Cons: Line-voltage wiring offers limited control options and flexibility, as circuiting/zones are relatively fixed. This type of wiring is usually required to be installed in some type of protected run, such as conduit. This can increase its installed cost relative to low voltage, with another cost consideration being copper prices. An electrician is also required to install it.

Low voltage wiring

Low-voltage (Class 2) wiring provides a pathway for power (10-24VDC) and communication/feedback for low-voltage control devices.

Pros: Most codes allow low-voltage wiring to be run without conduit and junction boxes, allowing it to be installed independent of the power wiring (e.g., laid on top of suspended ceiling tiles using plenum-rated conductors), resulting in dramatic gains in flexibility and allowing construction of sophisticated control systems involving layered lighting control as granular as individual light fixtures. It is safer to install and, in some cases, may not require an electrical trade to install it. And it is relatively easy to reconfigure based on future changes.

Cons: Unshielded low-voltage conductors can pick up electrical contamination in the environment—e.g., arc welding machines—or adjacent power conductors, particularly over longer runs. There may also be limits to the number of control devices that can be connected to the network. The potential for miswiring is higher than with line-voltage wiring.

“Ultimately, the decision on type of wiring should be a consequence of understanding the control requirements, space layout and end-user control needs,” says Eric Fournier, Director of Product Marketing for WattStopper. “For example, if the building owner is renting his office space and changing tenants on a regular basis with frequent modifications in furniture layout—i.e., conference room transformed into open office with cubicles—you will more than likely opt for low-voltage devices instead of line-voltage. But if the building owner needs automatic shutoff for a small private office—i.e., 12 ft x 12 ft—and line-voltage wiring is already present at the switch box location, you will more than likely use a stand-alone line-voltage occupancy sensor.”

Low voltage control wiring: analog versus digital

Dedicated low-voltage control wiring enables advanced flexibility and functionality in today’s lighting control systems. The most common types are analog 0-10VDC and digital.

Analog 0-10VDC: 0-10VDC wiring uses two wires with a 1-10V potential between them.

“Analog offers good signal resolution, enabling closer identification of actual conditions,” says Ronald Bryce, National Sales Manager for PLC-Multipoint, Inc. “For example, consider a photosensor. If a standard 0-10VDC photosensor is scaled to represent 0-250 footcandles (fc), each volt of the signal from the sensor—called the return signal—represents 25 fc. To deactivate the lights in a shopping mall, the control system normally turns them OFF at 7 fc. The return signal in this case would be 0.28VDC.”

However, Bryce adds, transferability of the signal is a disadvantage with analog. Because of the reference to 0V, the distance an analog signal can be sent is limited. This can be mitigated by using a 4-20mA signal instead of a 0-10VDC signal, although 4-20mA devices are generally more expensive and not all control systems can operate with these signals.

A common 0-10VDC wiring type is stranded-copper twisted-pair 18AWG wiring. The wiring is stranded copper because it provides a more stable current path (as DC signals tend to be transferred by the outer edges of the conductor) while being relatively easy to work with; solid wire is usually acceptable in low-voltage systems that use AC control power. Twisted-pair offers some protection against noise while being economical and able to be transported in bulk and easily cut in the field to required length. Typical sizes range from 22AWG to 14AWG, with 18AWG being typical; size can be increased for longer runs where voltage drop is a concern.

The wiring may be specified with shielding or no shielding. As low-voltage wiring is sensitive to electrical noise and electromagnetic interference, shielding provides a degree of immunity, and can be specified for environments where these issues may be a concern.

Other wiring types include shielded or unshielded CAT5 and CAT6 twisted-pair wiring, which offers good immunity against interference in electrically noisy environments.

“Zip lines, arranged like lamp cord, can be very economical and can serve the purpose for short hauls in electrically clean environments,” says Greg Bennorth, Director of System Projects for Universal Lighting Technologies. “Twisted pair, with or without shielding, maintains its impedance over long distances and has a certain amount of noise immunity, but can be expensive. Coaxial cable, although having good noise immunity and being relatively inexpensive, is not generally used in lighting control.”

Digital: Digital wiring uses two wires with a maximum potential of 18V between them. Very little current is drawn through the wires, unlike analog wiring, which sends commands based on a voltage level and therefore draws current. Instead, command and status information is transmitted as digital binary messages.

“Digital networking technology has revolutionized lighting controls allowing multiple energy management strategies to be deployed at the individual fixture level,” says Andrew Parker, PE, LC, Director of Sales for Encelium Technologies. “This technology is further merging lighting controls with other building systems to enhance capabilities through sharing of data to complete the intelligent building infrastructure.”

This produces several benefits:

• lower susceptibility to electrical and radio frequency interference;
• ability to be installed as Class 1 or Class 2 wiring, depending on the manufacturer;
• a large number of devices can be connected to the network;
• network communications are constantly flowing through the network both ways, and can be monitored or recorded as desired, allowing real-time collection of performance data for energy analysis and maintenance;
• single wiring bus connecting all control devices;
• light fixtures can be grouped and regrouped (zoned and rezoned) using software, with no wiring changes; and economical integration of multiple control devices/strategies.

These advantages are delivered using advanced circuitry in intelligent control devices and are often made available with preterminated connectors, which will impose a cost premium.

For digital devices to be able to communicate using digital messages, they must be able to speak the same language—that is, use the same communication protocol—such as DALI, proprietary, BACnet, LON, RS485, etc.

RS485 uses a twisted pair of small-gauge wires with a shield conductor and can be run up to 4,000 ft., but is often polarity sensitive and requires a linear topology. LON-based communication often uses an unshielded twisted pair, allowing open topology and not being polarity sensitive, but is limited to 1,500 ft. before a repeater is required. DALI-based systems use a simple pair of wires without a requirement for twisting, specific topology or polarity, but is limited in the number of nodes that can be connected to the system, and is criticized for being very slow in transmission speed. Some manufacturers have created proprietary protocols based on DALI, offering its advantages but mitigating its disadvantages. However, if a component fails, it must be replaced by a compatible device from the same manufacturer. Additionally, proprietary systems may not wire the same even though their components may perform similar functions, requiring special attention to manufacturer installation instructions.

Low voltage control wiring: prefabricated option

Structured wiring featuring factory-tested and verified cable assemblies has emerged as a premium option providing a significant alternative to the traditional approach of making point-to-point connections using bulk wire. L ow-voltage analog and digital wiring may be available with preterminated connections such as RJ45 (computer), RJ11 (telephone) or some proprietary type of connector. These systems are often offered with plug and play controls that automatically configure upon installation, enabling immediate operation.

The advantage of this approach is it can simplify installation and reduce errors related to incorrect terminations. On the other hand, wire lengths must be predetermined, and while there may be installation labor savings, the cost of materials is generally higher.

General principles

Architecture: Some systems require separate input networks from output networks. For example, light fixtures may be grouped to respond to system commands coming from a separate network of input devices made up of occupancy and photosensors, manual controls, etc.

Wiring class: Line- and low-voltage wiring systems imply different requirements in the field. Class 1 wiring can be installed in the same conduit, while most codes allow Class 2 to be installed outside of conduit. For analog systems, the manufacturer is likely to recommend that Class 2 wiring not be installed with Class 1 wiring in Class 1 conduit, so as to prevent electrical interference with the analog signal voltage.

Termination: Bulk wiring can be cut and terminated in the field, or the wiring can be delivered in specified lengths with preterminated connections.

Shielding: The wire may be specified as shielded or unshielded; shielding provides more protection against electrical interference presented by adjacent electrical wire or equipment. It is generally recommended that low-voltage DC signals be carried by shielded conductors.

Speed: Depending on the speed of transmission, wiring run lengths may be capped.

Loading: For analog systems, the amount of loading (current requirement) must be observed.

Topology: Some communication protocols are limited in available topologies (linear/daisy chaining, star, hub and spoke, etc.).

Control protocol: Wiring requirements may be different based on the type of control protocol used. For example, a system using RS485-based communication will have different wiring requirements than a system using LON or Ethernet.

Voltage drop: In analog systems, voltage drop issues may limit length or require boosters. Wire gauge (size) may be increased to compensate. Consult with the manufacturer.

Polarity: Most low-voltage wiring requires that polarity be maintained and not be able to be reversed.

Stranded vs. solid conductors: It is generally recommended that low-voltage DC signals be carried by stranded conductors. Solid wire is usually acceptable in low-voltage systems that use AC control power.

Verification: Determine if and how the wiring installation can be tested.
Redundancy: When running conductor bundles/cables over long distances, consider running spare conductors to mitigate the possibility of conductor breakage during installation.

Questions to ask about control wiring

What local codes and standards—such as requirements for conduit or plenum-rated jackets— apply to the project? If I exceed these standards, does the potential payback justify any additional costs?

When the system is in full operation, how much control does the building owner want occupants to have over levels and schedules? What is the level of technical sophistication of these occupants?

What level of flexibility and functionality is required from the control system, which will determine what controls are desired?

What is the sequence of operations for the controls in the system?
Is the control wiring Class 1 or Class 2?

Is the control wiring independent of the power wiring?

Is a twisted-pair configuration required to maintain impedance?

Will the wiring require shielding to prevent electromagnetic and radio frequency interference?

How far is the lighting device from its control? What is the maximum run length?

Is there a device or power limit for the wiring run or control?

What control protocol will be used?

What topology is desired?

Are specific connectors required?

Are the wiring requirements a simple matter of voltage drop, wire gauge and number of conductors?

If the local code allows Class 2 wiring to be installed in plenums, is the selected wiring plenum-rated?

How will the wiring network be tested and troubleshot?

Can the manufacturer provide detailed point-to-point schematics? How rigid is the specification in the event of changes in the field?

Are different ballast voltages allowed?

Are different lighting types—fluorescent, HID, LED—allowed?

Special thanks to the following Lighting Controls Association member representatives for their valuable contributions to this whitepaper (listed alphabetically by company):

Andrew Parker, PE, LC, Director of Sales for Encelium Technologies
Thomas Hinds, Product Manager-Fluorescent Dimming Ballasts for Lutron Electronics Co., Inc.
Ronald Bryce, National Sales Manager for PLC-Multipoint, Inc.
Greg Bennorth, Director of System Projects for Universal Lighting Technologies
Pete Baselici, Senior Product Line Manager for WattStopper
Eric Fournier, Director of Product Marketing for WattStopper

Liberty Property Trust Reduces Energy Consumption and Saves Money with Encelium Technologies’ Energy Control System

By Lighting Controls Association, on June 23, 2010

When one of the nation’s leading commercial developer of green office and industrial buildings sought to optimize the economic, energy and environmental performance of its Malvern, Pa.-based corporate headquarters, Liberty Property Trust partnered with Encelium Technologies to reduce overall lighting energy consumption by 60 percent. The real estate investment trust, which owns 77 million square feet of office and industrial space in more than 20 markets throughout the United States and the United Kingdom, used its 31,000-square-foot office building as a pilot demonstration site of Encelium’s highly advanced Energy Control System (ECS) for use in its other properties.

Originally tasked with the goal of reducing lighting energy consumption by 50 percent and delivering a payback from energy savings in less than five years, the installation of ECS yielded better-than-expected results. With an annual energy cost reduction of $10,383 or about $0.33/square foot, Liberty also achieved its payback goal in less than four years. (See case study: http://www.encelium.com/pdf/case-studies/EnceliumLibertyPropertyTrustCaseStudy.pdf)

“We wanted to use our own office space to evaluate the system and determine actual savings and whether advanced network lighting controls made sense for all of our properties,” said Fred Dougherty, Liberty’s vice president of portfolio technology. “We are very serious about reducing our carbon footprint, increasing energy performance and looking to potentially include this type of lighting control system on other LEED certification development activities.”

Liberty has almost 8 million square feet of LEED space completed or under construction nationwide. The company has been acknowledged with numerous industry awards for its initiatives to develop, retrofit and operate its buildings in an environmentally sensitive manner.

ECS seamlessly integrates and simultaneously deploys six user-friendly energy-management strategies facility-wide. These include personal controls, task tuning, daylight harvesting, smart time scheduling, occupancy sensing and load shedding. Utilizing Encelium’s Polaris software, Liberty was able to collect data on each energy management strategy, validate the savings and further optimize performance and dollar savings.

“ECS is ideal for retrofits or new construction for all buildings types, including office buildings, schools, healthcare and public facilities, parking garages, big-box retail, stadiums and warehouse space,” said Tony Marano, president and chief executive officer of Encelium Technologies. “Not only does the system create economic value and give property owners, managers and end-users unprecedented digital control, ECS also effectively and efficiently improves workplace ergonomics, occupant productivity and tenant satisfaction.”

As the most advanced lighting control solution for commercial buildings, ECS typically meets or exceeds today’s sustainable requirements for new or existing office buildings, including Title 24, ASHRAE 90.1 and is eligible for various utility rebate programs and local “green” building mandates. Designed to reduce lighting-related energy costs by 50 to 75 percent, the system also contributes between 12 to 18 points, depending on the application, toward achieving the coveted U.S. Green Building Council’s Leadership in Energy & Environmental Design (LEED).

Using the collaborative power of addressable networking technology in conjunction with advanced control hardware and software, ECS reduces lighting use and energy costs at a faster rate than other environmental measures and has an average payback on investment of two to five years. Since 2001, ECS has been installed in more than 25 million square feet of commercial space across North America and Europe. Encelium has posted a 200 percent annual growth increase during the last two years. Headquartered in Teaneck, N.J., the company also has operations in Canada and Europe.

For more information about Encelium Technologies, visit www.encelium.com.

Study: Controls Combine to Deliver Large, Persistent Energy Savings and Improved Occupant Satisfaction in Open Office

By Craig DiLouie, on December 13, 2007

What are the benefits of combining advanced lighting control strategies in the same space? Are the energy-saving benefits of lighting controls persistent over time? Can advanced lighting controls be successfully applied to open offices given concerns about jurisdiction conflicts, lighting uniformity, etc.? Can they enhance worker satisfaction?

A new office lighting field study addresses these questions. Involving about 90 workers in a real-world open-office environment, the one-year study determined that occupancy sensing, daylight harvesting and individual occupant dimming control worked together in the building to produce average energy savings of 47% while correlating with higher occupant environmental and job satisfaction.

The study demonstrates that sophisticated lighting control strategies can be combined successfully to generate persistent, large energy savings in open-plan offices while improving occupant satisfaction with their jobs and workspace.

“The industry has long sought objective evidence that lighting controls not only save energy, but also benefit organizations in other ways such as occupant satisfaction,” says Dr. Guy Newsham, senior research officer for National Research Council Canada – Institute for Research in Construction. “This research provides such evidence.”

The study

The one-year study occurred within four floors of an open-plan office building in Canada. The building selected for the project was attractive to the research team for several reasons. First, it contained a sophisticated control system operating in an open-plan office setting, an environment often perceived as unfriendly to sophisticated control strategies. Second, this control system combined three control strategies—occupancy sensing, daylight harvesting and individual dimming control. Third, the control system was already installed and in operation. Finally, the site manager was agreeable to the research team not only monitoring energy savings, but also surveying occupants on matters related to environmental and job satisfaction.

Four years earlier, the building had installed 195 direct/indirect lighting fixtures to replace 530 recessed 2×4 T8 deep-cell parabolic fixtures. The new fixtures, centered over the cubicle workstations and containing 3x32W T8 lamps powered by two electronic ballasts, reduced installed lighting wattage by about 40%.

The direct/indirect lighting system features advanced controls, while the parabolic system does not. Workers occupying 86 workstations on three and a half floors participated in the study by using the advanced controls, while workers on half of one floor were still using the old parabolic system, a setup that allowed a comparison between the two groups. Monitoring software was installed to collect detailed data for a period of one year.

“Our research group has had a strong interest in lighting controls over many years, and the opportunity to conduct a field study offered a great complement to the laboratory studies we’ve conducted,” Newsham points out. “There was almost no information available on the long-lasting success of energy-saving lighting control technologies when used in combination in real buildings. In addition, a field study allowed us to explore effects that simply can’t be addressed in anything but a real workplace, but such as those related to organizational productivity. I think everyone agrees that new technologies should demonstrate benefits for occupants and their organizations, as well as energy savings, and such outcomes will promote their adoption.”

The control system

The direct/indirect fixtures contained an integral occupancy sensor and photosensor. The center lamp, connected to a fixed-output electronic ballast, produced the indirect (uplight) component of the fixture; this ensured uniformity of light on the ceiling. The two outboard lamps, connected to a dimmable electronic ballast, produced the direct (downlight) component of the fixture; light output varied based on signals from four control inputs.

If the occupancy sensor detected vacancy in the workstation below, it signaled the dimming ballast to gradually dim the downlight (outboard) lamps until reaching 0% light output, at which point they were switched off. If the sensor detected occupancy, it signaled the ballast to start the lamps and restore light output to the last set level.

The photosensor monitored light levels on the below task plane, which received variable contributions from daylight available through windows. When light levels exceeded the occupant-set level, the photosensor signaled the dimming ballast to dim the downlight lamps.

Occupants could also dim the lamps forming the direct, or downlight, component of their lighting fixtures via an on-screen slider on their desktop PCs, thereby enabling them to choose their own preferred task light levels.

With this setup, researchers were able to study the overall effect of the combined control system, and estimate the relative contributions of each control type to the overall savings, for a period of one year. The study was conducted in three phases—phase 1 (39 workdays) with just the occupancy sensors and individual dimming controls active, and with a sensor time delay of 8 minutes with 7 minutes of dimming before shutoff; phase 2 (140 workdays) with all controls enabled, and with an occupancy sensor time delay of 12 minutes with 3 minutes of dimming before shutoff; and phase 3 (61 workdays), the same as phase 2 but with email reminders encouraging occupants to use the individual control feature in their workstations.

Just before the study was initiated, the control system was recalibrated. As new employees were hired and entered the study area, or existing employees were re-assigned, the IT department, responding to a request from the energy manager, quickly re-enabled the individual control feature, which would prove critical in sustaining this control strategy.

A fourth control strategy—global automatic on/off switching from a central point of control based on a daily schedule (7:30 AM to 5:00 PM workdays)—was in effect but not included in the study.

The results

By replacing the recessed parabolic fixtures with the direct/indirect fixtures, energy savings of about 40% were realized and lighting power density was reduced from about 0.92W/sq.ft. to about 0.54W/sq.ft.

The combined control system increased lighting energy savings to 67-69% compared to the old parabolic system. Further, the direct/indirect fixtures operating with the control system produced 42-47% energy savings compared to if the fixtures operated at full light output without the controls. All energy savings resulting from the use of the controls were accompanied by concomitant demand reductions. Because the controls ensured that not all lighting power was used at any one time, the average lighting power density in use was about 0.28W/sq.ft. The site manager estimated a simple payback for the advanced system, based on energy cost savings alone, to be 2-4 years in a new installation and 4-12 years in a retrofit installation.

If installed alone, the occupancy sensors would have produced an estimated average 35% savings, daylight harvesting 20% and individual dimming control 11%. Daylight harvesting savings were higher in perimeter workstations, as would be expected (due to closer proximity to windows), and the researchers estimate that savings would have matched the occupancy sensor savings if perimeter fixtures had been allowed to dim below 50% output based on the photosensor signal (deeper dimming based on occupancy sensors or personal control was allowed).

Occupant surveys demonstrated a correlation between the presence of the controls and higher job and environmental satisfaction. While individual dimming’s contribution to overall energy savings was relatively small, researchers credited the improvements in occupant satisfaction to the individual control feature. The researchers are currently looking deeper into the relationship between the controls and worker satisfaction, and hope to publish their results by 2009.

“This study demonstrates that the right package of controls, properly maintained, can produce large, persistent energy and demand savings coupled with benefits to occupants and their organizations, and refutes suggestions that these kinds of control systems cannot work well in open-plan offices,” concludes Newsham. “Although such systems do have a higher initial cost than standard office lighting systems, the overall benefits may justify the investment, especially in the context of other investments organizations make in their employees and their work environments.”

The field study was supported by the Government of Canada, BC Hydro Power Smart and Ledalite Architectural Products. To see the complete study, click here.

DALI and the Promise of Digital Dimming

By Craig DiLouie, on May 13, 2007

By Craig DiLouie and Rick Miller, PE

Rick Miller is President of RNM Engineering, Inc. and founder of the DALIbyDesign.us website.

Dimming of fluorescent lighting offers significant benefits in terms of supporting visual needs with good lighting, giving users control of their own lighting, and energy savings. The advent of digital dimming offers a new option with clear advantages over traditional analog dimming.

Digital dimming can be used almost anywhere that analog dimming can be used, for the same purposes: visual needs, personal control, daylight harvesting, scheduling and other control strategies. If fluorescent dimming is desirable for a given application, digital dimming can offer distinct advantages related to intelligence, flexibility and two-way communication.

Photo courtesy of Zumtobel

DALI is particularly well suited for:

Energy management applications such as scheduled automatic shutoff to meet energy codes, daylight harvesting, due to the ability to more economically set up very small control zones around the daylight aperture, and scheduling via a central computer, which allows load shedding, demand savings and potential utility incentives.
Supermarkets, some retail spaces and similar applications with frequent merchandise or layout changes.
Small and open offices where users are given dimming control over their own lighting as part of a strategy to increase worker satisfaction.
Conference rooms, classrooms, training rooms and similar spaces that require different lighting scenes for multiple types of use.
Larger installations with multiple buildings, where feedback on lighting component status can facilitate more efficient lighting maintenance.

Why DALI?

In any dimming system, the ballasts and controllers must be able to speak and hear the same language. In the case of digital dimming systems, this language is either proprietary—that is, unique to a particular manufacturer and, if allowed, other adopters—or an open standard: the Digital Addressable Lighting Interface (DALI) protocol. DALI, originally part of Europe’s Standard 60929, has been a NEMA Standard (243-2004) in the United States since 2004.

When examining whether to use DALI for a fluorescent dimming installation, one must first assess the pros and cons of digital control, and then weigh the pros and cons of DALI as the communication protocol that enables the digital components to talk to each other.

DIGITAL DIMMING

The HVAC industry began embracing Direct Digital Controls (DDC) in the early 1990s. With digital electronic ballasts, this technology is now available for lighting. Digital dimming offers a number of clear advantages compared to analog dimming. These advantages are:

Simplified wiring
High degree of granularity of control accuracy (flexibility)
Easy reconfiguring of control zones without rewiring
Two-way communication (some digital ballasts)

In a digital dimming system, a single set of control wires form a low-voltage control bus—sometimes (inappropriately) called a loop.

Creating the communication network

Compatible ballasts and controls (up to a total of 64 devices—with each ballast having its own unique stored address) connect to this bus in order to provide control signal interaction. For larger installations, multiple buses can be networked to proper scale. The control bus provides two-way communication; ballasts can both respond to commands and reply to queries.

Control options include centralized systems (a personal computer or building automation system) as well as local controls such as manual dimmers, occupancy sensors and photosensors.

The ballasts and controls connected to the same bus can be assigned to up to 16 layers (groups or zones) of controls and scenes in the same space, and later reconfigured, via programming.

Simplified wiring

A single pair of control wires, which form the bus, connect the ballasts and controls directly, which simplifies wiring in spaces with multiple control zones by reducing the number of homeruns.

The level of skilled labor is reduced because there is no need to pull wire according to a zoning schedule. Each ballast on the circuit is wired the same. There are no switch legs or three-way travelers. In addition, dimming control panels/modules are not needed to control light output. Instead, digital systems use a small power supply connected to the bus.

Digital ballasts can be wired into the lighting system using Class 1 or Class 2 wiring methods according to the National Electrical Code (NEC). Digital ballasts may use a Class 1-rated 5-conductor cable that uses one hot (live), one neutral, one ground and two polarity-insensitive control wires, all routed together in the same conduit. It is also possible to install the ballasts and controls as a Class 2 installation, in which case the control wires must be routed separate from the power wires. Check with the ballast and controls manufacturers whether their products are rated for Class 1 installation.

Conventional controls wiring scheme. Five separate lead runs from the wall controller are required in this example, creating wiring complexity. If the system must be changed in the future, rewiring is required. Graphic courtesy of Universal Lighting Technologies

Digital network wiring scheme. All ballasts are connected to the same lead runs, simplifying the wiring required. Rezoning and adding controllers are also simplified. Graphic courtesy of Universal Lighting Technologies

Flexibility

When configuring a fluorescent dimming system, the designer must specify control zones—that is, a fixture or group of fixtures that are controlled simultaneously by a single controller. For example, in a daylight harvesting scenario with windows, the designer may place lighting circuits parallel to the window, and set up each circuit as a separate control zone.

The smaller the control zones, the more granularity, or flexibility, can be achieved, and along with it higher energy savings. But cost also increases.

Digital lighting control provides the ultimate in flexibility. When using analog dimming systems, the smallest zone is a branch circuit. With a digital system, zoning is implemented using software, independent of circuits, using individual ballast addresses stored in memory. Because each ballast is individually addressable, control zones can be established that are as small as a single ballast or light fixture. Ballasts or fixtures can also be grouped to provide up to 16 layers of controls/scenes.

This enables:

Highly granular and responsive control
Ability to generate a wide variety of zones and scenes in any controlled space
Ability to adapt to changes over time and even be completely reconfigured without rewiring

For large installations, individual buses can be networked for the control of hundreds or even thousands of ballasts.

Two-way communication

Finally, the digital ballast includes a microprocessor that functions as storage (ballast address, intensity settings, fade rate), receiver (control signals) and sender (intensity, lamp/ballast status) of digital info rmation. DALI instructions such as GoToScene and SetMax are sent to the ballasts, utilizing the data stored in its microchip memory.

But the ballast is not only “smart,” it can also “talk back.” As the control bus enables two-way communication, the digital ballast can not only receive commands, but respond with maintenance and energy info rmation such as the status of the ballast and lamps.

This enables the lighting system operator to query ballasts for energy usage (using feedback such as IntensitySetting), which can be used for a variety of purposes from energy savings verification to benchmarking to billing internal departments or tenants individually for their lighting usage.

It also enables the operator to query ballasts for lamp and ballast failure (querying for a response such as BadLamp), which can improve the efficiency of lighting maintenance and improve customer service from the facilities department.

Scheduled switching

Lighting automation is now mandated in most of the United States. With the adoption of the ASHRAE/IES 90.1-1999 model energy code by the U.S. Department of Energy as the minimum national standard, a majority of state energy codes require automatic shut-off of all lighting in commercial buildings larger than 5,000 sq.ft. in size, with few exceptions.

Automatic shut-off can be provided by occupancy sensors and programmable time scheduling devices. According to the California Energy Commission, scheduled automatic shutoff can generate 5-15% energy savings.

With 0-10VDC dimming, the ballasts are connected with control wires; the controller can dim, but not switch, the lights. To achieve ON/OFF switching, the power wiring would have to be reconnected to match the dimming circuits.

With DALI-based digital lighting, any ballast or group of ballasts on the network can be given an ON/OFF or DIM command without rewiring the circuits.

This enables compliance with prevailing energy code requirements for automatic shutoff in controlled spaces without the need for a control panel with a scheduling function.

Buyer beware

The higher level of capabilities from digital control systems often entails tradeoffs in cost and complexity.

Higher component cost, but not necessarily higher installed cost

Digital ballasts and controls typically present a higher component cost largely due to power supply/router requirements, but they can present a lower installed cost due to a reduction in wiring labor for group and scene control, and the removal of the need for dimmer modules/control panels in larger installations.

More sophisticated programming and commissioning

Digital control also presents more sophisticated programming when centralized systems are used, and requires on-site field commissioning, which should be factored into the design specification so that the appropriate party is aware and can bid on this portion of the installation.

During the start-up phase, a database of ballast addresses, with physical locations and the control device that operates them, needs to be created and then maintained when the layout of the space changes. It may be advisable to involve the client’s IT staff in the creation and maintenance of the database.

THE DALI PROTOCOL

Once the designer decides to implement a digital control strategy, a primary choice is whether these devices should communicate using a proprietary protocol or DALI, which is a standard open protocol.

Proprietary protocols

The advantage of a proprietary protocol is that the complete control system can be furnished by a single manufacturer, which has tested all components to ensure interoperability and supports the entire system on the job.

The disadvantage is that the owner is tied to a single manufacturer, which limits choice and potentially sacrifices economy.

DALI is an open standard

DALI is a royalty-free, non-proprietary, two-way, open and interoperable digital protocol and a standard in the United States and Europe (European Standard 60929, NEMA 243-2004).

Currently in the U.S., DALI consists of a set of commands to and from ballasts within a defined data structure and specified electrical characteristics.

The advantages of DALI are that it:

Provides true interchangeability across ballasts and controls. Multiple manufacturers can be involved in a system, instead of being tied to a single supplier, using DALI as an open platform. This can result in lower costs, ensures future availability, and enables the system designer to select product functions from one manufacturer and combine them with products from other manufacturers.
Provides standardized ballast performance. For example, DALI defines light output for all levels of dimming signals. DALI ensures consistent dimming performance across all dimming ballasts regardless of type or manufacturer, currently not achievable with analog dimming methods such as 0-10VDC.

BALLASTS AND CONTROLS

As an open standard, DALI is supported by five major U.S. electronic ballast manufacturers and a growing number of controls manufacturers, which offer DALI-compatible products.

Ballasts

DALI-compatible fluorescent dimmable electronic ballasts are currently available in:

Universal input voltage (120VAC to 277VAC)
One-, two-, three- and four-lamp models for T8 lamps
One- and two-lamp models for CFL, T5 and T5HO lamps

Dimming range

Digital ballasts are available that provide a dimming range of 100% to 1%, utilizing a logarithmic dimming curve.

The inverse-square dimming curve is used for better control of the lighting intensity in response to the human perception of brightness.

Programmed start

Digital ballasts utilize programmed-start technology to maximize lamp service life, highly suitable for frequently switched applications such as installations with occupancy sensors.

Controls

DALI based digital control systems can include all controls that would normally be used for multi-scene fluorescent dimming, such as preset controls, as long as they are rated as compatible with DALI.

They can be used to operate with a DALI compatible digital ballasts for fluorescent lamp dimming, or a DALI compatible solid-state transformer for precise incandescent lamp dimming in both 120V and 12V versions.

Digital controls are also compatible with switching devices such as occupancy sensors and other devices such as photosensors.

Centralized and local control

With a digital control scheme, the designer can implement automation strategies such as scheduled dimming from a central PC for centralized control while enabling occupant control and override via local interfaces such as preset controllers or occupant PCs.

DALI-based digital control systems enable scene-control and multiple energy management strategies through a single space, entire building or multiple buildings. Graphic adapted from Tridonic and OSRAM SYLVANIA

Integration with LMS and BAS

The digital lighting network can be connected to a lighting automation or building automation system for integration with other lighting or building systems.

For a DALI-based digital control system to communicate with a non-DALI lighting control system, or a BAS operating using another protocol such as BACnet or LonWorks, a translator device, called a gateway, is required to enable these systems to communicate with each other.

SAMPLE APPLICATIONS

Below are two applications, a conference room and a lecture hall.

Conference room

Digital system in a conference room. Graphic courtesy of Universal Lighting Technologies

Components include:

(2) 1xF32T8 dimming ballasts (FL-1)
(2) 2xF28T8 dimming ballasts (FL-2)
(8) 1xCFQ26W dimming ballasts (CF)
(2) electronic halogen dimming modules (H)
(1) wall-mounted 4-scene recall controller (SC)
(1) handheld programmable remote (HH)
(1) power supply (PS)

In this space, light levels can be controlled so that the side of the room where presentations occur can receive more or less illumination depending on the media used. Halogen accent lights highlight pictures on two of the walls.

The 4-scene wall-mounted controller is used at the entrance. The handheld remote is used for zone programming as well as programming scenes and recall.

With 14 light sources in this room, most of them can be established as its own zone for a very high degree of flexiblity and control resolution.

Lecture hall

Digital system in a lecture hall. Graphic courtesy of Universal Lighting Technologies

Components include:

(18) 2xF32T8 dimming ballasts
(6) 1xCFM32W dimming ballasts
(1) ceiling-mounted IR sensor kit
(2) wall-mounted on/off, up/down controls
(1) handheld programmable remote control
(1) handheld remote with 4-scene recall
(1) power supply

In this space, control zones can be established so that during A/V presentations, the lights near the front of the hall can be dimmed while the lights in the rear can be set at higher levels.

A 4-scene handheld remote is used with the ceiling sensor for dimming control.

Controls at the doors provide both on/off and up/down control.

The programmable remote is used for programming and is then stored only with access to authorized users.

ASSESSMENT

Digital dimming is not for all applications, but it offers clear advantages in applications where fluorescent dimming is both well-suited and desired. As demand for fluorescent dimming increases, so will the demand for digital dimming increase as a control method that offers distinct benefits.

Digital dimming allows software configuration of lighting groups, presets matching the lighting to the space usage, and integrated energy management functions.

Digital systems can be configured as large networked systems requiring commissioning and training, or as simple stand-alone room preset dimming controls requiring no special tools or PCs.

As an open standard used with digital systems, DALI enables true interchangeability among vendor products and standardized performance across manufacturers.

Although digital systems can present a higher component cost, labor savings resulting from simplified wiring can result in a lower installed cost compared to 0-10VDC dimming.

And although digital dimming is new, and a little different, much of the equipment and methods will be familiar to designers and installers of 0-10VDC dimming systems. In several important ways, installation is actually simpler.

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